1. Field of Invention
The present invention relates to an assisting focusing method, and more particularly to an assisting focusing method for a face block.
2. Related Art
Auto focusing (AF) technology substantially includes active auto focus and the other is passive auto focus. In the active auto focus technology, a set of infrared emitters or laser emitters and corresponding receivers are used to project patterns of light on a photographed object and then a distance between a camera and the photographed object is calculated through a method such as triangulation, in which the distance is a focus. However, due to poor precision, the active auto focus cannot be applied in a situation that the image capture device and the photographed object are separated by an object such as glass. Furthermore, when using the active auto focus, additional light emitters and receivers need to be disposed in the camera, so that the cost is high.
In the passive auto focus, before practical photographing, many images are captured from micro focus to a region set to be infinite far and clarifies of the captured images are analyzed to determine the focus. In the passive auto focus method, only an image sensor and a calculating unit of the camera itself need to be used, so that manufacturing cost is reduced. However, due to a large amount of calculation, precision is usually sacrificed in the passive auto focus to avoid spending too much time on AF.
In recent years, in addition to professional photographers, more and more common users use digital cameras to photograph. Generally, images photographed by the common users usually have problems of being not in focus as a result of lacking photographing skills compared with professional photographers. However, when a picture is photographed, a human image is usually an important part in a picture. In a conventional AF method, a problem that a background or other objects instead of human might be determined as photographing subjects but the human that should be the photographing emphasis are defocused. Furthermore, once the precision of the AF is insufficient, and a focusing error occurs, the photographed image may be seriously blurred. Especially, when the photographed image is a human image, photographing defects that occur on the face seem even worse.